Much of Showtime’s original programming falls into the trap of over-reliance on a central conceit, without which they generally struggle, having little substance outside that conceit on which to build a thematically strong story. “Dexter” would have little to stand on if the title character swore off serial killing, and if suburban mom Nancy Botwin ditched the pot business for good, “Weeds” would certainly flounder.

However, Showtime’s new paranoid political thriller “Homeland” defies that reliance. It is a subtly crafted show that expertly balances its many themes — the ethicality of government surveillance, Americans’ perception of Islam and its relationship with terrorism, the crippling mental effect of war on soldiers — with both ambiguity and delicacy, while also carrying off some spectacular plotting and character twists.

“Homeland” centers on Carrie Matheson (Claire Danes), a young CIA agent who, although doggedly committed to her job, is emotionally and mentally unstable. Carrie lives with the unending guilt over not having caught a clue that might have prevented the 9/11 attacks and this guilt both motivates and handicaps her work.

When Carrie is given a tip from an interrogation subject that an American solider has turned to al-Qaida, she immediately zeroes in on Sgt. Nicholas Brody (Damian Lewis), a recently recovered American prisoner of war who spent eight years being interrogated by the Iraqi regime of Abu Nazir (a fictional and vaguely bin Laden-like terrorist leader). Carrie uses all the government power she can scrounge up to investigate Brody, beginning by setting up a surveillance system in his house and scrutinizing his every move.

In contrast with all the political intrigue involved in “Homeland,” the show also manages to make its portrayal of its characters’ domestic lives just as compelling. Carrie’s slow descent into paranoia, fueled by her as-yet unnamed mental illness builds tension, and Danes’s manic portrayal of a woman consumed in turns by jittery paranoia, self-doubt and fierce righteousness is blistering. Sgt. Brody’s wife Jessica’s (Morena Baccarin) indecision over whether or not to tell Nick that she’s fallen in love with his best friend while she took him for dead in his absence is also anguishing.

It’s the delicate ambiguity with which “Homeland” treats subjects like American surveillance, mental illness and the revelation of Brody’s conversion to Islam that make the show so remarkable. Paradoxically, the show’s hesitance to make any hard-and-fast moral statements about these subjects make “Homeland” all the more bold in its ambivalent assessment of post-9/11 America.

The show also sets itself apart by constantly defying viewers’ expectations about the typical twists and turns of a political thriller. For instance, any other serial drama might have drawn out Carrie’s surveillance of the Brody household for an entire season. However, the show dispenses with this plot device within four episodes as Carrie’s warrant expires, forcing her into more and more morally dubious situations in order to keep track of Brody.

Now that “Homeland” has been officially renewed for a second season and Showtime has confirmed that the enigmatic P.O.W. Sgt. Brody will be present for at least another season, it’s all the more uncertain what direction “Homeland” will take in seasons to come. Luckily for us, uncertainty is what “Homeland” does best.

Published on Friday, November 18, 2011 as: Showtime finds success with political thriller